Endpoint detection window, chemical mechanical polishing pad with window and preparation method thereof

ABSTRACT

The present invention relates to B24B, and more specifically, the present invention relates to an endpoint detection window, a chemical mechanical polishing pad with a window and a preparation method thereof. A side surface of the window is provided with a plurality of circumferential grooves. In the present invention, a column-shaped window with a specially designed side surface structure is provided and subjected to integrated pouring and molding with a polishing pad to manufacture a chemical mechanical polishing pad having high bonding strength between the window and the polishing pad. As a side surface of the window is of a multi-groove structure, not only is the bonding contact area between the window and the pad increased, but also a convex structure is formed by a polishing pad body material poured into the grooves so as to form an embedded bonding manner with a groove structure of a window material.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is based upon and claims priority to Chinese patent application No. 202210804155.5, filed on Jul. 7, 2022, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to B24B, and more specifically, the present invention relates to an endpoint detection window, a chemical mechanical polishing pad with a window and a preparation method thereof.

BACKGROUND

Chemical mechanical polishing pads are one of key consumable materials used in processes for manufacturing of semiconductor chips, and polishing endpoint detection windows are one of important structures of the chemical mechanical polishing pads. Polishing pad windows and polishing pads are generally bonded in two ways. The one way includes using a heat-sensitive adhesive or a pressure-sensitive adhesive to realize bonding. The other way includes placing window materials in molds to undergo integrated pouring with polishing pad materials and burying and wrapping the peripheries of the windows by the polishing pad materials to realize bonding.

At present, the research on the polishing pads and the windows is mainly focused on their materials. For example, a chemical mechanical (CMP) polishing pad for polishing such as a semiconductor substrate is provided in CN108723983B. The chemical mechanical polishing pad is provided with one or more of endpoint detection windows (windows) having a thickness of less than 2 mm for truncating ultraviolet (UV) at a wavelength of 325 nm or below. However, few improvements have been made to a window structure, and the window used is generally designed to have a smooth surface in contact with the polishing pad, as shown in FIG. 1 .

However, chemical mechanical polishing pads with windows having smooth contact surfaces manufactured by the above traditional methods usually have the situation that the windows and the polishing pads are not tightly bonded during processing and using, leading to gaps, cracks and even falling at joints of the windows, so as to cause leakage of polishing solutions and other problems.

SUMMARY

In order to solve the above problems, the first aspect of the present invention is to provide an endpoint detection window. A side surface of the window is provided with a plurality of circumferential grooves, and the maximum circumferential depression depth (R) of the grooves is 0.5-3 mm and may be listed as 0.5 mm, 0.8 mm, 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2 mm, 2.2 mm, 2.5 mm, 2.8 mm and 3 mm. The maximum circumferential depression depth of the grooves is the maximum depression distance of the grooves in a direction parallel to an exposed surface.

As a preferred technical solution of the present invention, the maximum radial width (L) of the grooves is equal to or greater than R. The maximum radial width is the maximum edge distance of the grooves in a direction perpendicular to the exposed surface.

As a preferred technical solution of the present invention, the maximum radial width (L) of the grooves is equal to or less than 5R.

As a preferred technical solution of the present invention, the depression area of the grooves is equal to or greater than (2−π/2)R².

As a preferred technical solution of the present invention, the depression area of the grooves is equal to or less than 2R². Preferably, the depression area is equal to or less than R², and the depression area is the area obtained after the grooves are removed in a radial section diagram. For example, when the grooves are semicircles, the depression area is (2−π/2)R².

As a preferred technical solution of the present invention, the shape of the grooves is selected from one or more of an arc, a polygon and a wave shape.

As a preferred technical solution of the present invention, the polygon is selected from one or more of a triangle, a rectangle and a zigzag. When the shape of the grooves is a triangle, the angle of the hypotenuse and circumference of the triangle is 30-65° and may be listed as 30°, 40°, 45°, 60° and 65°.

As a preferred technical solution of the present invention, the distance (H) of adjacent edges of the adjacent grooves is 0-5R and may be listed as 0, 0.5R, 1R, 1.5R and 2R. The distance of adjacent edges is the distance of the closest edges of the adjacent grooves.

As a preferred technical solution of the present invention, the roughness of an exposed surface of the window is 0.1-10 Ra and may be listed as 0.1 Ra, 0.5 Ra, 1 Ra, 1.5 Ra, 2 Ra, 3 Ra, 4 Ra and 5 Ra.

As a preferred technical solution of the present invention, the shape of the exposed surface of the window is selected from one or more of a circle, an ellipse and a rounded rectangle. The size of the exposed surface is not specifically limited in the present invention, and the exposed surface may be selected according to polishing needs in order to be exposed on one surface of a polishing pad. For example, when the exposed surface is a circle, the diameter of the exposed surface is 15-80 mm. When the exposed surface is an ellipse or a rounded rectangle, the diameter of a long side is 60-80 mm, and the diameter of a short side is 15-25 mm. The shape of the window of the present invention is a column, such as a cylinder or a prism, where the prism may be a cuboid and the like.

The second aspect of the present invention is to provide a chemical mechanical polishing pad with a window, where the chemical mechanical polishing pad is provided with the endpoint detection window.

The third aspect of the present invention is to provide a preparation method of the chemical mechanical polishing pad with a window, where the chemical mechanical polishing pad is prepared by integrated pouring. The window and a polishing pad body are not specified in material in the present invention and are both prepared from a polyurethane material. The preparation method of the polishing pad specifically includes: placing a window in a mold, adding raw materials for preparation of a polishing pad body, performing integrated pouring and molding to obtain a mixture, and cutting the mixture to a suitable thickness, such as 2 mm, followed by surface processing treatment, such as mechanical processing to control the roughness and flatness of the surfaces of the polishing pad body and the window.

Compared with the prior art, the present invention has the following beneficial effects.

-   -   (1) In the present invention, a column-shaped window with a         specially designed side surface structure is provided and         subjected to integrated pouring and molding with a polishing pad         to manufacture a chemical mechanical polishing pad having high         bonding strength between the window and the polishing pad. As a         side surface of the column-shaped window is of a multi-groove         structure formed by machine processing, not only is the bonding         contact area between the window and the polishing pad increased,         but also a convex structure is formed by a polishing pad body         material poured into the grooves after curing molding so as to         form an embedded bonding manner with a groove structure of a         window material, thereby greatly improving the bonding strength         between the polishing pad and the window.     -   (2) In addition, the inventor has found that controlling the         relationship between the depression area and the depression         depth (R) of the grooves is conducive to the stability of the         embedded structure. When the depression area is small, the         polishing pad body material is difficult to form firm bonding         with the grooves. Moreover, the inventor has also found that the         thickness of the grooves should not be too large, otherwise gaps         between the grooves and the polishing pad body are increased,         which is not conducive to firm bonding of the two materials.     -   (3) In addition, the inventor has also found that the radial         distance of the grooves will affect whether cracks and other         problems occur during polishing. When the radial width and the         circumferential depth are controlled in an appropriate         proportion and the depression area of the grooves is controlled         to be not small, the stability of the window can be promoted         during polishing, damage caused by displacement, cracks and         other problems of the polishing pad to the window is avoided,         and the service life of the polishing pad is prolonged.     -   (4) Furthermore, in order to improve the bonding strength         between the window and the polishing pad, surface treatment may         be performed on the contact surface of the column-shaped window         material. Meanwhile, the compatibility and wettability between         the surface and the polishing pad material are improved, and         damage caused to the joint of the window and the polishing pad         during polishing is also reduced by appropriate roughness.     -   (5) According to the window and the polishing pad provided by         the present invention, gaps, cracks and falling of windows and         even leakage of polishing solutions and other risks caused by         traditional bonding manners of windows and polishing pads are         avoided, the bonding strength between the polishing pad and the         window is improved, and the yield and durability of the         polishing pad are improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a cross section of a traditional polishing pad;

FIG. 2 is a schematic diagram of a cross section of a window provided in Example 1;

FIG. 3 is a schematic diagram of a front view of the window provided in Example 1;

FIG. 4 is a schematic diagram showing bonding of a polishing pad and a window in Example 2;

FIG. 5 is a schematic diagram showing an enlarged local structure of the window in Example 2;

FIG. 6 is a schematic diagram showing bonding of a polishing pad and a window in Example 3;

FIG. 7 is a schematic diagram showing bonding of a polishing pad and a window in Example 4; and in the figures, 1 refers to a groove, and 2 refers to an exposed surface.

DETAILED DESCRIPTION OF THE EMBODIMENTS Examples Example 1

As shown in FIG. 2 to FIG. 3 , this example provides a window. A side surface of the window is provided with a plurality of circumferential grooves 1, the maximum circumferential depression depth (R) of the grooves 1 is 0.5 mm, the maximum radial width (L) of the grooves 1 is 0.5 mm, and the depression area of the grooves 1 is 0.25 mm². The shape of the grooves 1 is selected from a rectangle, the distance (H) of adjacent edges of the adjacent grooves 1 is 0.5 mm, and the roughness of an exposed surface 2 of the window is 1 Ra. The shape of the exposed surface 2 is a rounded rectangle, the diameter of a long side is 60 mm, and the diameter of a short side is 15 mm.

Example 2

As shown in FIG. 4 to FIG. 5 , this example provides a window. A side surface of the window is provided with a plurality of circumferential grooves 1, the maximum circumferential depression depth (R) of the grooves 1 is 3 mm, the maximum radial width (L) of the grooves 1 is 3 mm, and the depression area of the grooves 1 is 9 mm². The shape of the grooves 1 is a rectangle, the distance (H) of adjacent edges of the adjacent grooves 1 is 3 mm, and the roughness of an exposed surface 2 of the window is 5 Ra. The shape of the exposed surface 2 is a rounded rectangle, the diameter of a long side is 80 mm, and the diameter of a short side is 25 mm.

Example 3

As shown in FIG. 6 , this example provides a window. A side surface of the window is provided with a plurality of circumferential grooves 1, the maximum circumferential depression depth (R) of the grooves 1 is 1 mm, the maximum radial width (L) of the grooves 1 is 1 mm, and the depression area of the grooves 1 is 0.43 mm². The shape of the grooves 1 is a semicircle, the distance (H) of adjacent edges of the adjacent grooves 1 is 0 mm, and the roughness of an exposed surface 2 of the window is 4 Ra. The shape of the exposed surface 2 is a rounded rectangle, the diameter of a long side is 70 mm, and the diameter of a short side is 20 mm.

Example 4

As shown in FIG. 7 , this example provides a window. A side surface of the window is provided with a plurality of circumferential grooves 1, the maximum circumferential depression depth (R) of the grooves 1 is 1 mm, the maximum radial width (L) of the grooves 1 is 1 mm, and the depression area of the grooves 1 is 0.5 mm². The shape of the grooves 1 is a triangle, the angle of the hypotenuse and circumference of the triangle is 45°, the distance (H) of adjacent edges of the adjacent grooves 1 is 0 mm, and the roughness of an exposed surface 2 of the window is 4 Ra. The shape of the exposed surface 2 is a rounded rectangle, the diameter of a long side is 70 mm, and the diameter of a short side is 20 mm.

Performance Evaluation

1. Performance test of an endpoint detection window: Polishing research was carried out by using Anji A28 copper abrasive slurry on a single-module integrated CMP polishing machine of Hangzhou SIZONE Electronic Technology Inc. A 10 kA bare copper wafer was used as a test wafer (moniter wafer) to determine a polishing pad with an endpoint detection window. Unless otherwise specified, polishing conditions used in all polishing experiments are as follows: a polishing platform at a rotation speed of 93 rpm; a polishing head at a rotation speed of 87 rpm; and a polishing solution at a flow rate of 170 mL/min. According to the endpoint detection window, the polishing time was controlled to 40-60 s/wafer. More than 100 wafers were polished in the experiment. After the polishing pad was used, the polishing pad was taken down to check the window position of the polishing pad. It can be confirmed that the window with a grooved edge is not prone to the phenomena of falling and leakage during polishing.

The bonding situation of a window and a polishing pad is judged through evaluation of the bonding strength between the window and the polishing pad.

Evaluation of the bonding strength: Two kinds of samples were used in the experiment, one is a traditional polishing pad with a smooth and flat endpoint detection window (control sample), and the other one is a polishing pad with a window as described in the present patent. Connected parts of the polishing pads and the windows were cut and prepared into test samples having a width of 1 cm and a length of 8 cm. Each sample involved the window at one end and the polishing pad at the other end. The two ends of each sample were clamped by a 200 kg sensor tensile machine to test the maximum load for separation of the window and the polishing pad of the sample.

TABLE 1 Sample Maximum load/pound force name First sample Second sample Third sample Control 22.38 10.61 21.25 sample Example 1 130.40 100.60 116.43 Example 2 99.73 102.31 97.65 Example 3 76.53 65.41 78.32 Example 4 97.34 94.39 93.87

According to test results in Table 1, it can be seen that the window provided by the present invention has better bonding strength with a polishing pad body, and meanwhile, the phenomenon of falling of the endpoint detection window of the polishing pad caused by a poor bonding force is avoided, thereby greatly improving the use effect of the polishing pad. 

What is claimed is:
 1. An endpoint detection window, wherein a side surface of the window is provided with a plurality of circumferential grooves, and the maximum circumferential depression depth (R) of the grooves is 0.5-3 mm.
 2. The endpoint detection window of claim 1, wherein the maximum radial width (L) of the grooves is equal to or greater than R.
 3. The endpoint detection window of claim 1, wherein the depression area of the grooves is equal to or less than 2R².
 4. The endpoint detection window of claim 1, wherein the maximum radial width (L) of the grooves is equal to or less than 5R.
 5. The endpoint detection window of claim 1, wherein the shape of the grooves is selected from one or more of an arc, a polygon and a wave shape; and the polygon is selected from one or more of a triangle, a rectangle and a zigzag.
 6. The endpoint detection window of claim 1, wherein the distance (H) of adjacent edges of the adjacent grooves is 0-5R.
 7. The endpoint detection window of claim 1, wherein the roughness of an exposed surface of the window is 0.1-10 Ra.
 8. The endpoint detection window of claim 1, wherein the shape of the exposed surface of the window is selected from one or more of a circle, an ellipse and a rounded rectangle.
 9. A chemical mechanical polishing pad with a window, wherein the chemical mechanical polishing pad is provided with the endpoint detection window of claim
 1. 10. A preparation method of the chemical mechanical polishing pad with a window of claim 9, wherein the chemical mechanical polishing pad is prepared by integrated pouring. 